Question: Solve for $r$ : $25 + r = 23$
Answer: Subtract $25$ from both sides: $ \begin{eqnarray} \\ 25 + r &=& 23 \\ \\ {-25} && {-25} \end{eqnarray} $ $ \begin{eqnarray} \hphantom{25 + r} &\hphantom{=}& \hphantom{23} \\ r &=& 23 {- 25} \\ \end{eqnarray} $ Simplify. $ r = -2$